Transducer construction employin employing annular vibrators



Sept. 29, 1959 L. w. cAMP 2,906,991

TRANSDUCER CONSTRUCTION EMPLOYING ANNULAR VIBRATORS Filed June 2'7, 1955Ilia? INVENTOR. Leon W Camp /7 ATTORNEY 2,906,991 TRANSDUCERCONSTRUCTION EMPLOYING ANNULAR VIBRATORS Leon W. Camp, Glendale, Calif.,assignor to Bendix Aviation Corporation, North Hollywood, Calif., acorporation of Delaware Application .lune 27, 1955, Serial No. 518,316 7Claims. (Cl. 340-8) This invention relates to underwater transducers ofthe type employing one or more radially vibratile annular vibrators, theinner faces of which are in acoustic conductive relation with the waterand the outer faces of which are acoustically insulated from the water.Certain features of the invention are also applicable to transducers inwhich the outer face of an annular vibrator is in contact with the waterand the inner face is acoustically insulated from the water.

An object of the invention is to simplify the construction and improvethe eiiiciency of transducers of the type mentioned.

A more specic object is to improve the acoustic insulation of thenon-working surface of the annular vibrator.

Another specilic object is to provide a transducer constructionpermitting the use of free air or other gas as the acoustic insulatingmedium in contact with the inactive or non-working surface of an annularvibratile element.

Other more specific objects and features of the invention will appearfrom the description to follow.

In transducers employing annular vibratile elements, as usuallyconstructed, one end of each vibrator is closed by a wall of radicallydilferent impedance from water to reiiect sound, and the other end isopen so that the inner annular surface is communicated with the water.Since radially vibratile rings also radiate from their peripheral faces,the latter must be acoustically insulated from the water. Furthermore,when the rings are of ceramic materials having electrodes on their innerand outer walls, the walls must be electrically insulated from eachother. Acoustic and electrical insulation has been accomplished in thepast by providing a sound-conductive liquid barrier (sound window) asthe front wall of the transducer, iilling the transducer with anelectrically insulating liquid having substantially the same acousticproperties as water, and surrounding the outer faces or walls of theannular vibrators with an acoustic insulating material, such as air cellrubber, Corprene, etc.

The present invention eliminates the use of both the sound window andthe solid insulating material by sealing between the ends of the annularvibrators and the casing so that the inner surfaces of the vibrators areexposed directly to the water, whereas the outer surfaces are separatedfrom each other and from the casing by air space. The seal must be ofsuch a nature as to permit the radial vibration of the vibrators, andthis condition is satisfied by employing a rubber O-ring positionedbetween each end of each vibrator and the adjacent end wall of thetransducer casing.

A full understanding of the invention may be had from the followingdetailed descripion with reference to the drawing, in which:

Fig. l is a front end elevational view of a complete transducer inaccordance with the invention employing seven annular vibratileelements.

Fig. 2 is a front end elevational view with the front wall removed.

States Patent ice Fig. 3 is an enlarged detail longitudinal sectiontaken in the plane III-III of Fig. l.

Fig. 4 is an end view, showing a single annular transducer in accordancewith the invention adapted to receive or transmit at its externalcylindrical face.

Fig. S is a longitudinal section in the plane V--V of Fig. 4.

Referring to Figs. l, 2 and 3, the transducer therein disclosedcomprises a front wall 10a, a rear wall 10b, and a cylindrical lateralwall 10c, together defining a casing 10. The front wall 10a and the rearwall 10b are rigidly secured in iixed spaced relations parallel to eachother by a plurality of screws 11 which extend through aperturesprovided therefor in the front wall 10 and are threaded into the rearwall 10b. Each screw 11 is surrounded by a rigid metal sleeve 12 whichdetermines the spacing between the walls 10a and 10b when the screws aredrawn up tight. The peripheral wall 10c is so dimensioned as to beclamped tightly between the front and rear walls at the edges thereof. Arubber seal 19 may be provided between the ends of the peripheral wall10c and the front and rear walls 10a and 10b respectively.

The casing 10 contains an array of seven annular vibratile elements 13,each having flat parallel end walls 13a and 13b, respectively, acylindrical inner wall 13C, and a cylindrical outer wall 13d. Eachelement 13 has an inner electrode 13e on its inner cylindrical face 13eand an outer electrode 13]c on its outer cylindrical face 13d.Connection to the inner electrodes 13e may be made by connecting eachelectrode to the casing as by a pigtail 14. The outer electrodes 13]ccan be connected by leads to each other and to the central conductor 15aof a coaxial lead-in-cable 15, the outer conductor 15b of which isgrounded to the casing 10.

Each element may be of an electromechanically sensitive material, suchas barium titanate, which is capable of vibrating radially in responseto electrical potential applied between the inner and outer electrodes13e and 133, or, vice versa, is capable of generating a potentialbetween said electrodes when vibration is induced mechanically. However,the present invention does not relate to any particularelectromechanically-sensitive material, but rather to an assemblyincorporating radially vibratile rings, regardless of the exact natureof the elements themselves.

The upper end 13a of each element 13 is sealed with respect to the frontwall 10a by an O-ring 16 of rubber or other suitable elastomer mountedin an annular groove, either in the casing end wall 10a or the upper endwall 13a of the element. lt is usually easier to form the groove in thecasing wall 10a, and such an arrangement is shown inFig. 3. The lowerend 13b of the vibratile element is similarly sealed with respect to thecasing Wall 10b by an O-ring 17.

The front end wall 10a of the casing 10 is provided with seven apertures18, each aligned with and substantially coextensive with the inner wall13C of its associated vibratile element. Hence, the interior surface orwall 13e of each vibratile element is in direct communication with waterexterior of the casing, whereas the outside walls 13d of all thevibratile elements are acoustically isolated from each other and fromthe casing by a dead air space defined by the vibratile element and thecasing. This dead air space provides about the best possible acousticinsulation to acoustically insulate the outer surfaces of the vibratileelements.

Although the 0-rings 16 and 17 provide suicient freedom of movement tosubstantially unappreciably impede the acoustic vibration in radial modeof the vibrators 13, they offer substantial frictional resistance tolarge displacements of the elements from their desired positionsv in.alignment with. the, openings. 18. However,J

as additional precaution to. prevent such displacement of the annularelements, thev posts 11 are positioned adjacent the; outerr sui-.facesl13d off the; elements. lf3 and. are surrounded with tubes of yieldablematerial 2u" of such thickness as.: to: lightly contact: the, outersurfaces i3d of the; Vibratile elements. and thereby prevent anyappreciable movement thereof away from their predetermined positions:v

A transducer having an array of vibratile element-s, as shown. in Figs.l, 2- and 3, is particularly usefui where itc i's. desired to; havedirectional properties; Le., to transmit or receive` sound.` mosteiciently in a certain direction. However, there areoccasions where itis desirable to, transmit. or receive. sound. simultaneously in allhorizontal directions.. A desirable form of transducer for this purpnse.isasinglefradially'vibratile annular element having its; outercylindrical wall in. acousticl conductive relation. with; the) waterfand its inner wall. acoustically insulated'.V Such. an arrangement' inaccordance wtih the presenti invention is. shown in Figs..4. and 5.. Itwill be observed that the construction is` essentially the same as` thatin Figs. 1,. 2. and 31, except'that. therev is only one radiallyvibratile annular element, and both Vof its ends are closed by casingplates. 25 and. 26 of.` substantially. the same diameter as the externaldiameter of the annular element 1'3., thev end plates having groovestherein.` and OS-.rings 16. and` 17 corresponding to the O-ring seals inFig. 3. However, the twofendplates 25 and 26 are solid,wso. that theyde'ne with the. element 1-3 a. closed cylindrical air space. whichacoustically insulates the. inner wall 13C. Bolts 11, spacer sleeves 12,and locating sleeves 20 identical with those shown in Fig. 3 areemployed inV Fig..4, but'they arepositioned within the annular element13. so thaty they extend through the dead air space therein.

Although for thepurposeof` explaining the invention a particularembodiments thereof has been shown and described, obvious modificationswill occur toV a `person skilled inthe art,A and I do not desire to belimited` to theexactfdetails shown and described.

I claim: v

1'. A transducer foruse inliquids comprising: a radially vibratileannular element of electromechanically-sensitive materia-l having fiatparallel opposite end'. walls and inner and outer cylindrical walls;means associatedrwith said element fon electrically coupling it to anelectric, circuit; casing means. defining with said annular element aclosed air space. acoustically isolating the outer cylindrical wall ofsaid element and including a pair of casing end walls juxtaposedtobutspaced from the respective end walls ofsaid element, and anelastomer sealing ring compressed between. each endwall of saidl annularelement and the adjacent casing end wall for effecting a iluid seal`there- 4' of said end wallshas. an opening therethrough aligned withsaid element for acoustically. communicating the inner surface thereofwith the exterior of said casing.

3. A transducer according to claim l in which said casing means includesa plurality of rigid post members extending betweenv said end walls; ofsaid casing through said, closed air space for rigidly supporting saidcasing end' Walls spaced, apart av distance slightly exceeding' thelength of said annular element.

4. A- transducer according to: claim 3 in. which one ofV saidjuxtaposedendi walls. at. each. end of said element has an annular groove thereinand saidi sealing ringf'is an Orring positioned partly in andpartlyprojecting from said groove". v

5. A transducer according to; claim 3 in which said post members arepositioned adjacent said outer wall of said element and yieldable meanssupported by said posts and contacting relativelyA small areas. oi saidouter wall for supporting' said annular Velement against lateral=displacement. A

6. Liquid-vibrating apparatus comprising: a radially vibratile annular:element of electromechanically-sensitive materialhaving-.at parallekopposite end faces, and inner' and' outer generally cylindricalA faces;means associated with saidelernent: for electrically coupling it to; anelectric circuit; casing means for supporting said element for radialvibrationz and forming a liquid. barrien between the said inner and.outer cylindrical faces; thereon, said casing means comprising a pair ofcasing end walls juxtaposed tothe respective. end faces off said.element, each said end wall having-..a n. annular groove thereinopposite and of less radial width. thangthe' associated endl face ofsaid element;. an. elastomer sealing ring in each saidr groove.

of suchthickness; as; to1 projecty from the; groove against thevassociatedflat end face of said element; means'rigidly.

supporting said end walls with respect to each other and:

inspacedrelation torsaid: element such asfto: slightly compress each.said/ ringLbetween the .bottom of its groovev and the. associated endface of said element, saidl rings constitutingthe solemeansaxially.supporting said element with. respect. to said.casing;means;. andmeansother than saidl elastomer rings for limitingi transverse. movement ofsaidrelement wtih. respect. to said casing end walls.

7*.. Apparatus accordingLto claim.. 6. in which said elastomer: rings.area-rings, and; saidi spacing between saidV endl walls'isisuchiastolslightly attensaid. G-.rings whereby they effect a uids seal betweensaidV end wallsV and said end faces of; said element' while olering.only slight between While permitting radial vibration of the element Yrelative@ to said casing means.

'2'.` A'. transducer according to claim 1 in which one resstanceto.radial vibrationlof. said element. with respect to. saidfend walls.

ReferencesfCited-in; the leof this patent UNITED STATES, PATENTS Y2,732,536. MillerA f Jan. 24;.17`956

